Four United Nations peacekeepers were killed Friday when suspected jihadists staged a major attack on their camp in Aguelhok, northern Mali, the UN mission said.

Hopes that soldiers behind Mali's coup would swiftly restore civilian rule and tackle jihadism and ethnic violence are fading fast as the army expands its role.

A second batch of jihadists has been freed in Mali, sources said Tuesday, boosting speculation that a French charity worker and Malian politician held by the insurgents may be freed in a swap.

Mali's military junta will hold meetings on Saturday to discuss its promised transition to civilian rule after mounting pressure from neighbours to yield power in the weeks since it overthrew the nation's leader. 

The junta that seized power in Mali wants a military-led transitional body to rule for three years and has agreed to release the ousted president, a source in a visiting West African delegation and the rebel soldiers said Sunday.

Mali's president announced his resignation late Tuesday, just hours after armed soldiers seized him from his home in a dramatic power grab following months of protests demanding his ouster.

The news of President Ibrahim Boubacar Keita's departure was met with jubilation by anti-government demonstrators and alarm by former colonial ruler France, and other allies and foreign nations.

Eighteen UN troops and two civilians were wounded Thursday in a mortar attack on a military base in northern Mali, a UN official said, in fresh violence in the war-torn West African country.

Canadian personnel participating in the UN peacekeeping force in Mali will remain in place until the end of August, a month longer than planned, to ensure a smooth transition, the government said Friday.

Mali's prime minister resigned along with his entire government on Thursday following criticism over their handling of an upsurge of violence in the centre of the country and a massacre last month that left 160 people dead.

Nearly three months after a disputed presidential run-off, Malians will go to the polls again in legislative elections on October 28, officials have announced.